You were right Jim. Again. LOL! I'm not sure what the problem was, I re-leveled, re-did the cubes and still had the problem. Nozzle was reading .005mm at center of bed. Finally got frustrated and just started turning the Z screw, printing, turning, printing until it just seemed to fall into place. Whew! Frustrating.

Thanks for all the replies:) My next question is, if I calibrated with 0.2mm layer height, then change the setting to 0.25mm layer height, do I need to re-calibrate? Or the software will adapt that change automatically?

The slicer will adjust the extruder speed to push out the proper volume of plastic to fill whatever thread width x thickness you specify, so in that sense it's an automagic adjustment. However, the actual extrusion process is strongly nonlinear, so the 25% change from 0.20 to 0.25 mm thickness might require more (or less!) than a 25% change in extruder speed.

The Extrusion Multiplier is basically a fudge factor that compensates for all those nonlinear effects, but it should be pretty close within a "reasonable" range of variations. If you care about the results, sprinkle a couple of thinwall calibration boxes over the platform, slice & print 'em with the new thickness, and measure the results.

If they come out close enough for your needs, you're done. If not, well, you know what to do! [grin]

The slicer will adjust the extruder speed to push out the proper volume of plastic to fill whatever thread width x thickness you specify, so in that sense it's an automagic adjustment. However, the actual extrusion process is strongly nonlinear, so the 25% change from 0.20 to 0.25 mm thickness might require more (or less!) than a 25% change in extruder speed.

The Extrusion Multiplier is basically a fudge factor that compensates for all those nonlinear effects, but it should be pretty close within a "reasonable" range of variations. If you care about the results, sprinkle a couple of thinwall calibration boxes over the platform, slice & print 'em with the new thickness, and measure the results.

If they come out close enough for your needs, you're done. If not, well, you know what to do! [grin]